Leukocyte binding to the endothelium is a requisite first step in athe emigration of these blood-borne cells into tissue during atherosclerosis, inflammation and would healing. The overall objective of this research project is to better understand the intracellular signaling pathways and stimulated gene expression that are involved in leukocyte adhesion to endothelial cells (RS). The expression of leukocyte adhesion molecule is one functional marker of the agonist-induced, or "activated" state of EC. Our working hypothesis is that the activated state of EC. Our working hypothesis is that the activated state of EC is induced by cytokines and injury-associated modulators, such as thrombin, through a cascade of specific intracellular events including the activation of specific second messenger systems and the induction of multiple "early response" genes. We plan to test in this funding period the hypothesis that the latter include members of the homebox gene family of "master control" transcription factors. Secondly, we hypothesize that alpha-thrombin exerts its stimulatory effect on the transcription of the leukocyte adhesion molecule E-selectin via a mechanism distinct from that employed by cytokines. Finally, we hypothesize that a cascade of events occur within EC as a result of leukocyte adhesion, including changes in transcription factor levels and gene expression. Our first aim is to characterize further the molecular mechanism by which thrombin induces the transcription of the E- selectin gene. We will analyze the thrombin promoter using both transfected reporter gene constructs and gel shift assays. Secondly, we plan to characterize the regulation of expression of homeobox genes that we have recently cloned from EC cDNA libraries. Two of these genes, which encode known homeodomain proteins, are up- (Hox A9) or down- (Hox B2) regulated in response to EC activating agents. We will determine whether these or other homeodomain proteins play a role in the activation or proliferation of EC. Finally, we propose to characterize changes in transcription factor activation that occur in EC in response to co- incubation with leukocytes. We will pursue our recent observation that co- incubation (adhesion?) of monocytic cell with cytokine-treated EC results in a marked reduction in the level of NF-kappaB in the EC nuclei. We believe our findings will be directly relevant to the pathophysiological mechanisms underlying various inflammatory disease processes, including atherosclerotic plaque development, and have t he potential to identify novel therapeutic paradigms for these diseases.